Magnetic garnet materials are of interest, e.g., in the manufacture of magneto-optic and magnetic domain devices, and their usefulness as epitaxially grown layers and as bulk crystals has been demonstrated for a variety of compositions. Of particular interest are magnetic garnet layers which are epitaxially grown on a nonmagnetic substrate; such layers play a key role in magnetic domain devices, i.e., devices in which information is represented by the presence or absence of microscopically small magnetic domains or "bubbles" which are nucleated and propagated in response to variation of a magnetic field. Magnetic domain devices have been developed, e.g., as memory devices in which domain movement typically is in loop-shaped patterns which serve as shift registers; suitable patterns may be defined, e.g., by metallic overlays or by ion-implanted regions in the magnetic layer.
Continuing development effort in the field of magnetic domain technology has led to the realization of a variety of devices, some of which are suitable for operation under adverse conditions such as conditions of elevated temperature or else of very low temperature. In this respect, bismuth-containing garnet materials have been found to be particularly advantageous as disclosed in U.S. Pat. No. 4,419,417, issued Dec. 6, 1983 to R. C. Le Craw et al.
Also, there is continuing interest in reducing magnetic domain size while maintaining or increasing domain wall mobility, and this, in turn, calls for increased magnetic anisotropy in a magnetic layer. Magnetic anisotropy is understood to have two additive components, namely strain-induced anisotropy (due to lattice mismatch between a substrate and a grown film) and growth-induced anisotropy (resulting from compositional ordering of the film). Furthermore, it is known that in the case of bismuth-containing garnets, growth-induced anisotropy is directly related to the degree of undercooling of a melt from which a film is grown, so that it has been possible to achieve high magnetic anisotropy by epitaxial growth from melts at high levels of undercooling. It has been realized, however, that high levels of undercooling have an adverse effect on production yields, and means are sought for producing high growth-induced anisotropy in magnetic layers grown from a melt at relatively low degrees of undercooling.